(a) Field of the Invention
The present invention relates to an oscillator using spin transfer torque. More particularly, the present invention relates to an oscillator using spin transfer torque in a magnetic tunnel junction.
(b) Description of the Related Art
Controlling the magnetization of a magnetic layer by Spin Transfer Torque (STT) has been recently studied in order to implement a high density electronic circuit. According to the aforementioned method, conduction electrons spin-polarized by a pinned magnetic layer pass through a non-magnetic layer and then spin angular momentum of the conduction electrons is transferred to a free magnetic layer. As a consequence, the magnetization of free layer, for example, in a magnetoresistive device such as a magnetic tunnel junction (MTJ) is controlled. When the STT transferred by the conduction electrons is balanced with inherent damping torque of the free magnetic layer, which is in the opposite direction, the magnetization of the free magnetic layer can have a steady precession. If the magneto-resistance characteristic of the device is combined with the precession, a high frequency oscillation signal can be obtained. The frequency of the oscillation signal ranges from several GHz to several tens of GHz.
As described above, a typical oscillator using the STT includes a pinned magnetic layer, a non-magnetic layer, and a free magnetic layer. When a current larger than a threshold value and an external magnetic field are simultaneously applied to the oscillator, the oscillator generates a high frequency alternating current signal. The magnetization of the free magnetic layer rotates with a frequency of several GHz to several tens of GHz.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.